Caleb Rackliffe created CASSANDRA-19107:
-------------------------------------------
Summary: Revert unnecessary read lock acquisition when reading
ring version in TokenMetadata introduced in CASSANDRA-16286
Key: CASSANDRA-19107
URL: https://issues.apache.org/jira/browse/CASSANDRA-19107
Project: Cassandra
Issue Type: Improvement
Components: Legacy/Distributed Metadata
Reporter: Caleb Rackliffe
Assignee: Caleb Rackliffe
CASSANDRA-16286 achieved its goal of making sure that concurrent increments to
the ring version would independently increment the version (i.e. not "merge"
multiple invalidations into single versions), but it also unnecessarily
replaced the volatile read on {{ringVersion}} w/ making {{readVersion}}
non-volatile and acquiring the read lock on the fair {{ReadWriteLock}} in
{{TokenMetadata}}. This can result in unnecessary queueing w/ high CPU
usage/read volume. For example, you might see this on a 4.0 cluster...
{noformat}
"Native-Transport-Requests-99" #271 daemon prio=5 os_prio=0 cpu=5822566.56ms
elapsed=19477779.40s tid=0x00007fcc96c31b00 nid=0xb7bd waiting on condition
[0x00007fcb7f144000]
java.lang.Thread.State: WAITING (parking)
at jdk.internal.misc.Unsafe.park(java.base@11.0.16/Native Method)
- parking to wait for <0x00000005c0ab92a0> (a
java.util.concurrent.locks.ReentrantReadWriteLock$FairSync)
at
java.util.concurrent.locks.LockSupport.park(java.base@11.0.16/LockSupport.java:194)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(java.base@11.0.16/AbstractQueuedSynchronizer.java:885)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireShared(java.base@11.0.16/AbstractQueuedSynchronizer.java:1009)
at
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireShared(java.base@11.0.16/AbstractQueuedSynchronizer.java:1324)
at
java.util.concurrent.locks.ReentrantReadWriteLock$ReadLock.lock(java.base@11.0.16/ReentrantReadWriteLock.java:738)
at
org.apache.cassandra.locator.TokenMetadata.getRingVersion(TokenMetadata.java:1389)
at
org.apache.cassandra.locator.AbstractReplicationStrategy.getCachedReplicas(AbstractReplicationStrategy.java:82)
at
org.apache.cassandra.locator.AbstractReplicationStrategy.getNaturalReplicas(AbstractReplicationStrategy.java:116)
at
org.apache.cassandra.locator.AbstractReplicationStrategy.getNaturalReplicasForToken(AbstractReplicationStrategy.java:109)
at
org.apache.cassandra.locator.ReplicaLayout.forTokenWriteLiveAndDown(ReplicaLayout.java:209)
at
org.apache.cassandra.locator.ReplicaPlans.forWrite(ReplicaPlans.java:328)
at
org.apache.cassandra.service.StorageProxy.performWrite(StorageProxy.java:1426)
at
org.apache.cassandra.service.StorageProxy.mutate(StorageProxy.java:937)
{noformat}
Reverting to a volatile read makes this no longer possible, but keeps the fix
from CASSANDRA-16286 intact.
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